Felt making process



Patented June 20, 1939 FELT MAKING PROCESS Pierre Drewsen, San'dusky,Ohio, assignor to The Barrett Company, New York, N. Y., a corporation ofNew Jersey No Drawing. Application November 16, 1935, Serial'No. 50,153

2 Claims.

This invention relates to felt, more particularly to building felt,adapted to be saturated with waterproofing compounds such as asphalt,coal tar, coal tar pitch or other bituminous 5 waterproofing material,to form substantially waterproof products for building sheathing,roofing, fioor coverings and other constructional purposes. Thisapplication is a continuation-in-part of my copending application SerialNo. 86,098,

1 filed February 4, 1926, now Patent No. 2,029,310,

granted February 4, 1936, and is particularly directed to building feltsmade from fibers, preferably strength fibers, mixed with straw fiberstreated under conditions such that the straw fibers have sufficientabsorptive capacity, to-

gether with strength and hardness properties, to produce a felt whichmay be saturated with bitumen or other waterproofing material, and whichfelt has the balanced characteristics of strength, hardnessandsaturating capacity required for felts employed for roofing, sheathing,

fioor coverings and other constructional purposes.

The invention claimed herein constitutes a species divisible from thespecies claimed in parent Patent No. 2,029,310.

Heretofore the manufacture of felt intended to be saturated withwaterproofing compounds, such as melted bitumen, has usually beenaccomplished by employing one or more of the following as raw materials:

(1) Bags which contain substantially a mixture of cotton and wool;

(2) Rags consisting substantially of cotton;

(3) Rags which contain jute fiber in the form of waste bagging;

(4) Rags which contain old carpets composed largely of jute withquantities of cotton and wool;

(5) Rags which contain rag clippings of all grades with varying amountsof paper; and

(6) Paper stock composed largely of waste paper.

These materials are partially disintegrated in rag cutters andthereafter, while in suspension in water, are beaten in paper millheaters, then jordaned if desired, and finally formed into a continuoussheet on Fourdrinier or cylinder paper makingrnachines.

Rags are a relatively expensive raw material and the use 'of substantialproportions of the same in the manufacture of felt results in arelatively expensive product.

Paper stock is a less expensive raw material than rags, but the use oflarge, quantities of this material in the manufacture of felt tends toharden fibered in a beating engine; (1)) raw jute or jute or stiffen thefelt sheets excessively and render them unsuitable for many purposes.

In my co-pending application Serial No. 86,098 I have disclosed themanufacture of felt by mixing strength fibers, highly absorptive fibersand 5 filler fibers, which results in a felt eminently satisfactory forconstructional purposes. Examples of strength fibers given in myco-pending application are: (a) jute, that is waste bagging otherwisecalled N0. 3 rags, cooked by the calcium pentasulphite processsubstantially as described in United States Patent No. 996,225to ViggoDrewsen granted June 27, 1911, then washed until free from spent cookingliquors and afterward delo bagging cooked at an elevated temperature of130 to 150 C. in a solution of sodium carbonate containing about ten percent by weight of sodium carbonate based on the weight of the raw fiberbeing cooked (aten per cent solution of lime may be used instead of thesodium carbonate solution); (c) fiax tow made from American or Canadianflax straw by. the well known ,breaking process, by which the shive orinterior woody portion is largelyremoved; (d) jute or flax tow treatedin a beating engine with water at to C. to which approximately 10 percent alkali, such as caustic soda, lime, etc., based upon the dry weightof the fiber to-be treated, has been added, followed by thorough washingwith water of the fiber thus produced before it is used as a componentin the felt; (e) unbleached sulphite pulp; and (f) kraft pulp. v

As absorptive fibers the following are disclosed: (a) spruce or hemlockchips or shavings, cooked by the above mentionedcalcium pentasulphideprocess or by the sodium pentasulphide process, followed bythedisintegration into fibers by edge runners or in a beating or Jordanengine; (b) wood fibers treated at an elevated temperature of 90 to 100C; in a beating engine in a solution containing ten per cent of causticsoda based on the weight of the wood material or other alkali solution,followed by the washing of the fibers and their disintegration in abeating engine; (0) wheat straw, rye straw, oat straw, rice straw,barley straw or other cereal or annual crop fibers treated in a digesterwith water at elevated temperatures, for example, from to C. for a shortperiod of timeto thoroughly soak the 50 fibrous material, followed bydisintegration into fibers in a beating engine; (d) such straw ,or othercereal or annual crop fibers beaten at lower temperatures, for example,90 to 100 C.; or (e) at about 50 C. in a 10 per cent (based on the rweight of the straw) sodium carbonate solution; or (f) at atmospherictemperature in a caustic soda solution; and (g) cotton hull fiber,namely, minute seed hairs obtained from cotton seed hulls after removalof the cotton and cotton linters, containing a substantial proportion ofhull particles, cooked in accordance with the calcium or sodiumpentasulphide process, followed by the beating of the resultant fibers.

The following examples of filler fibers are iven: wheat straw, ryestraw, oat straw, rice straw, barley straw, cooked by the calcium orsodium pentasulphide' process, followed by the washing of the cookedfibers to free them from spent alkaline liquors and the beating of thewashed fibers; (b) such straw fibers cooked at an elevated temperatureand pressure in sodium carbonate, caustic soda or other alkali solutionand afterward washed and beaten and such straw fibers cooked and beatenin a beating engine at 90 to 100 C. in the presence of about ten percent of caustic soda based on the weight of the straw.

The function of the filler fibers is (a) to control the degreeofsaturation of the sheet and (b) to impart hardness thereto. Their use isparticularly advantageous in the production of felt when considerablehardness and medium saturating capacity is desired. In general increaseof filler-fiber content increases hardness and decreases saturatingcapacity.

I have also disclwed that certain of the fibers produced as hereinabovedescribed and primarily adapted to serve as filler fibers also havesufficient absorptive capacity so that when admixed with other fibers,such as the strength fibers, a sheet is produced having an intermediatecapacity for absorbing waterproofing material and considerably increasedhardness; such a sheet is especially adapted for making sheathing paperand bitumen-saturated felt-base floor coverings.

This application is particularly directed to the mixing of such fillerfibers and other fibers and to the resultant felt.

Filler fibers having suflicient absorptive capacity to adapt them foruse in making relatively hard felts to be saturated with bitumen forconstructional purposes, disclosed in my copending application are,wheat straw, rye straw, oat straw, rice straw, barley straw or otherlike straws cooked at an elevated temperature and pressure in sodiumcarbonate, caustic soda or other alkali solution. Such fibers may beproduced by cooking the aforementioned straws in a beating enginecontaining a solution of ten per cent of caustic soda based on theweight of the straw, while maintaining a .temperature of 90 to'100" C.in the beater. The time of beating and cooking the straw will depend onmany factors such as the strength of the alkaline solution in which thestraw is treated, the amount of the charge of straw introduced into thecooker, the temperature of the solution, etc., and the cooking andbeating should be carried out until the fibers are disintegrated to thedesired extent, which can be determined by inspecting and testing thefibers in the beater and cooker,

Any of the strength fibers hereinabove enumerated, which it will benoted are non-straw fibers, may be mixed with such straw filler fibers(a) cereal or other crop fibers such as to produce the desired felt. Oneexample of a felt made by mixing such filler fibers and strength fibersgiven in the specification of my co-pending application is as follows:15 per cent cooked jute fiber or cooked flax tow, mixed with 85% cookedstraw fibers resulted in a felt which would absorb at leastapproximately 100 per cent, based on the dry weight of the felt, of taror other bituminous waterproofing material.

It will be noted that, in accordance with the invention claimed in thisapplication, straw fibers are treated under conditions of increasedseverity as compared with the treatment of such fibers disclosed in myaforementioned co-pending application to produce absorptive fibers, thatis to say, the temperature of the treatment of the straw fibers ismaterially increased or the strength of the alkali employed in thetreatment is increased as compared with the temperature or strength ofalkalis respectively employed in pro-- ducing highly absorptive fibers.Thus there are produced fibers which, while less absorptive than thehighly absorptive fibers produced under milder conditions of treatment,have suflicient absorptive capacity and strength properties so that theycan be used in the formation of felts which can be waterproofed andemployed for roofing, flooring and other constructional purposes. Inaccordance with the claimed invention herein, it is not necessary totreat different batches of straw under different conditions, one moredrastic than the other, to produce both absorptive and filler fibers,but by one treatment, preferably of intermediate severity, a fiber isproduced from straw which has suflicient absorptive capacity andstrength characteristics so that it may be employed along with otherfibers such as strength fbers and without the use of highly absorptivefibers to produce an eminently satisfactory felt for constructionalpurposes.

It is to be understood that the above description is to be interpretedas illustrative and not in a limiting sense, and that this invention isnot restricted to the present disclosure otherwise than as is defined bythe appended claims.

I claim: I

1. A process of producing felt which comprises cooking straw in acaustic soda solution containing about 10% of caustic soda based on theweight of the straw maintained at a temperature of about 90 to 100 C. toproduce straw fibers imparting both hardness and absorptivecharacteristics to a sheet in which they are incorporated, mixing saidstraw fibers with strength fibers produced from wood and forming theresultant mixture of fibers into a felt sheet consisting entirely ofsaid straw and strength fibers.

2. A process of producing felt which comprises treating straw from thegroup, wheat straw, rye

straw, oat straw, rice straw and barley straw, in a solution containingabout 10 per cent of caustic soda based on the weight of the straw at atemperature of about 90 to 100 C. to produce fibers imparting bothhardness and absorptive characteristics to a sheet in which they areincorporated, mixing said straw fibers with strength fibers producedfrom wood, and forming the resultant mixture of fiber's into a feltsh'eet confibers.

PIERRE DREWSEN.

